Aegis
🦀 🏠 🍎 🪟 🐧 - AI-agent admission-control MCP server: validates file edits against Ring 0 syntax + Ring 0.5 structural
What is Aegis?
Aegis is a Model Context Protocol (MCP) server that allows AI assistants like Claude, Cursor, and VS Code to 🦀 🏠 🍎 🪟 🐧 - ai-agent admission-control mcp server: validates file edits against ring 0 syntax + ring 0.5 structural
🦀 🏠 🍎 🪟 🐧 - AI-agent admission-control MCP server: validates file edits against Ring 0 syntax + Ring 0.5 structural
This server falls under the Security category on MCPgee, the world's largest MCP server directory with 33,000+ servers.
Features
- MCP protocol support
Use Cases
Maintainer
Works with
Installation
NPM
npx -y @getaegis/cliPIP
pip install agent-aegisManual Installation
npx -y @getaegis/cliConfiguration
Configuration Details
claude_desktop_config.json
Performance
Response Metrics
Resource Usage
How to Set Up and Use Aegis
Aegis is an AI-agent admission-control MCP server written in Rust that validates proposed file edits before they are written to disk. It exposes a single validate_file tool that runs tree-sitter syntax checks (Ring 0) and 16 structural/security anti-pattern rules (Ring 0.5) — including detection of eval/exec usage, hardcoded secrets, and weak cryptography — returning structured findings so the agent can decide whether to proceed. Because Aegis requires no LLM calls of its own and has zero external dependencies, it adds near-zero latency to an agent's edit loop while providing a meaningful safety backstop against common coding errors.
Prerequisites
- Rust toolchain 1.74 or later (install via https://rustup.rs)
- Git (to clone the repository)
- An MCP-compatible AI client such as Claude Code, Cursor, or Cline
- No external API keys or accounts required
Clone the Aegis repository
Clone the repository from GitHub to get the source code and crate definitions.
git clone https://github.com/wei9072/aegis
cd aegisBuild and install the MCP binary
Use cargo to compile and install the aegis-mcp binary to your Cargo bin directory (~/.cargo/bin). This makes the binary available on your PATH.
cargo install --path crates/aegis-mcpVerify the binary is available
Confirm the aegis-mcp binary was installed correctly.
aegis-mcp --versionConfigure your MCP client
Add Aegis to your MCP client configuration. The server communicates over stdio and requires no arguments or environment variables.
{
"mcpServers": {
"aegis": {
"command": "aegis-mcp",
"args": []
}
}
}Use the validate_file tool in your agent workflow
Instruct your AI agent to call validate_file before writing any file change. The tool accepts the file path, proposed new content, optional old content for delta calculation, and optional workspace_root for cross-file analysis. It returns structured findings across syntax, signal, security, and workspace categories — with no severity verdicts so the agent can apply its own policy.
Aegis Examples
Client configuration (Claude Code)
Add this to your Claude Code MCP configuration. The aegis-mcp binary must be on PATH after cargo install.
{
"mcpServers": {
"aegis": {
"command": "aegis-mcp",
"args": []
}
}
}Prompts to try
Example prompts that leverage Aegis admission control in an agent coding session.
- "Before saving this file, validate it with Aegis and show me any security findings"
- "Validate the proposed changes to src/auth.py and report any hardcoded secrets detected"
- "Check my new database connection code for structural anti-patterns before writing it"
- "Run validate_file on this script and tell me if there are any eval/exec usages I should remove"Troubleshooting Aegis
cargo install fails with a linker error or missing system library
On Linux, install the build-essential package (sudo apt install build-essential). On macOS, install Xcode Command Line Tools (xcode-select --install). Then retry cargo install --path crates/aegis-mcp.
The agent calls validate_file but findings are empty even for obviously bad code
Ensure the file's language is one supported by the bundled tree-sitter grammars (Rust, Python, TypeScript, JavaScript, Go, C/C++ are common). Files with unknown extensions may not trigger syntax rules. Also confirm you are passing the full proposed content as new_content, not a diff.
Workspace-level findings (cross-file cycles, removed symbols) are not appearing
Pass the workspace_root parameter pointing to the repository root when calling validate_file. Without this parameter, Aegis operates in single-file mode and skips workspace-scope checks.
Frequently Asked Questions about Aegis
What is Aegis?
Aegis is a Model Context Protocol (MCP) server that 🦀 🏠 🍎 🪟 🐧 - ai-agent admission-control mcp server: validates file edits against ring 0 syntax + ring 0.5 structural It connects AI assistants to external tools and data sources through a standardized interface.
How do I install Aegis?
Install via npm with the command: npx -y @getaegis/cli. Then add the server configuration to your AI client's JSON config file (e.g., claude_desktop_config.json or .cursor/mcp.json).
Which AI clients work with Aegis?
Aegis works with all major MCP-compatible AI clients including Claude Desktop, Claude Code, Cursor, VS Code (GitHub Copilot), Windsurf, and Cline.
Is Aegis free to use?
Yes, Aegis is open source and available under the MIT License license. You can use it freely in both personal and commercial projects.
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